Bash Range: Sequence Expression Syntax and Examples

The Bash sequence expression generates a range of integers or characters by defining a start and end point. It is most commonly used in for loops to iterate over a numeric or alphabetic range without writing out each value manually.

This guide covers the sequence expression syntax, step increments, zero-padding, character ranges, practical loop examples, and how to work with dynamic ranges using variables.

Bash Sequence Expression Syntax #

The sequence expression takes the following form:

{START..END[..INCREMENT]}

• The expression begins with an opening brace and ends with a closing brace.
• START and END can be either positive integers or single characters.
• The START and END values are mandatory and separated with two dots .., with no space between them.
• The INCREMENT value is optional. If present, it must be separated from the END value with two dots .., with no space between them.
• The expression expands to each number or character between START and END, including the provided values.
• An incorrectly formed expression is left unchanged.

Integer Ranges #

Here is the expression in action — generating a range from 0 to 3:

echo {0..3}

0 1 2 3

If START is greater than END, the expression creates a decrementing range:

echo {3..0}

3 2 1 0

Character Ranges #

The sequence expression also works with single characters. The following example prints the lowercase alphabet:

echo {a..z}

a b c d e f g h i j k l m n o p q r s t u v w x y z

When characters are given, the expression expands in lexicographic order. You can also use uppercase letters:

echo {A..Z}

Increment and Step #

When an INCREMENT is given, it sets the step between each generated value:

for i in {0..20..5}
do
  echo "Number: $i"
done

Number: 0
Number: 5
Number: 10
Number: 15
Number: 20

You can use a negative increment to step down:

for i in {10..0..2}
do
  echo "Number: $i"
done

Number: 10
Number: 8
Number: 6
Number: 4
Number: 2
Number: 0

Leading Zeros #

When using integers, you can force each number to have the same width by prefixing START or END with a leading zero:

for i in {00..5}
do
  echo "Number: $i"
done

Number: 00
Number: 01
Number: 02
Number: 03
Number: 04
Number: 05

Prefix and Suffix #

The expression can be combined with static text before or after the braces:

echo file{01..4}.txt

file01.txt file02.txt file03.txt file04.txt

This is useful for generating file names, directory names, or any pattern that includes a numeric suffix.

Using Ranges in for Loops #

The sequence expression is most commonly used in for loops. The following example iterates from 1 to 5 and prints each value:

If you are looking for the Bash equivalent of Python’s for i in range(...), brace expansion is the simplest option for fixed ranges.

for i in {1..5}
do
  echo "Iteration: $i"
done

Iteration: 1
Iteration: 2
Iteration: 3
Iteration: 4
Iteration: 5

A common use case is creating a set of numbered directories:

for i in {1..5}
do
  mkdir "backup_$i"
done

This creates backup_1 through backup_5 in the current directory.

Variable Ranges with seq #

A common point of confusion is that Bash does not expand variables inside brace expressions. If you try to use a variable as START or END, the brace expression is left unexpanded:

START=1
END=5
echo {$START..$END}

{1..5}

The literal string {1..5} is printed instead of the expanded range. This is a Bash limitation — brace expansion happens before variable substitution.

To use a dynamic range, use the seq command instead:

START=1
END=5
for i in $(seq $START $END)
do
  echo "Number: $i"
done

Number: 1
Number: 2
Number: 3
Number: 4
Number: 5

seq also accepts a step argument:

for i in $(seq 0 2 10)
do
  echo "Number: $i"
done

Number: 0
Number: 2
Number: 4
Number: 6
Number: 8
Number: 10

Another option for variable ranges is a C-style for loop, which supports variables directly:

START=1
END=5
for ((i=START; i<=END; i++))
do
  echo "Number: $i"
done

Both seq and the C-style loop work reliably with variables. Use whichever reads more clearly for your script.

Practical Examples #

Countdown timer

for i in {10..1}
do
  echo "$i..."
  sleep 1
done
echo "Done"

Generate test files

for i in {1..10}
do
  touch "testfile_${i}.log"
done

Print columns of the alphabet

for c in {a..z}
do
  printf "%s " "$c"
done
echo

Create numbered backups

for i in {01..07}
do
  cp config.conf "config_backup_${i}.conf"
done

Quick Reference #

FAQ #

Why does {$START..$END} not work?
Brace expansion in Bash happens before variable substitution, so {$START..$END} is treated as a literal string rather than a range. Use seq $START $END inside a command substitution, or use a C-style for ((i=START; i<=END; i++)) loop instead.

What is the difference between {1..5} and seq 1 5?
{1..5} is a pure Bash brace expansion — fast and with no external command. seq 1 5 is an external command that prints numbers to standard output, one per line. The main practical difference is that brace expansion does not support variables, while seq does.

Can I use the sequence expression with strings longer than one character?
No. The sequence expression only supports single characters or integers. For multi-character strings you need a different approach, such as an array or a loop over a list.

How do I create a reverse or countdown range?
Set START higher than END: {5..1}. With an increment, use {10..0..2} to step down by 2.

Can I use the sequence expression outside of for loops?
Yes. echo {1..5} prints the expanded values space-separated on a single line. You can also use it in command arguments, file globs, or anywhere Bash performs brace expansion — for example mkdir dir{1..5} creates five directories at once.

Conclusion #

Use {START..END} for fixed ranges in loops and brace expansions. When you need a dynamic range driven by variables, reach for seq $START $END or a C-style for ((i=START; i<=END; i++)) loop. For more on Bash loops, see the Bash for loop guide .

About the authors

Dejan Panovski

Dejan Panovski is the founder of Linuxize, an RHCSA-certified Linux system administrator and DevOps engineer based in Skopje, Macedonia. Author of 800+ Linux tutorials with 20+ years of experience turning complex Linux tasks into clear, reliable guides.

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